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Chemistry > Carbonyl Compounds > Flashcards

Carbonyl Compounds Flashcards

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1
Q

Two isometric ketones are shown below.

( Q = CH3COCH2CH2CH3 )
( R = CH3CH2COCH2CH3 )
( Both are in displayed formula around the functional group )

Name and outline a mechanism for the reaction of compound Q with HCN and name the product formed.

A

Name of mechanism:

  • Nucleophilic addition

Mechanism:

  • ( ^-CN, with lone pair of electrons, attacks the delta positive carbon attached to the O )
  • ( Arrow is drawn from the lone pair on CN to the carbon )
  • ( Arrow is drawn from the double bond in C = O to the oxygen )
  • ( The oxygen now has a lone pair of electrons and a negative charge )
  • ( The lone pair of electrons move to a H^+ which is freely in the “ Solution “ creating a O - H bond )
  • The product is CH3CNOHCH2CH2CH3

Name of product:

  • 2-hydroxy-2-methylpentanenitrile
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2
Q

Some students were asked to suggest methods to distinguish between isomers Q and R.
One student suggested testing the optical activity of the products formed when Q and R were reacted separately with HCN.
By considering the optical activity of these products formed from Q and R, explain by this method with not distinguish between Q and R.

( Q = CH3COCH2CH2CH3 )
( R = CH3CH2COCH2CH3 )

A
  • R is inactive
  • Q is a racemic mixture
  • Racemic mixture is inactive
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3
Q

Write an equation for the formation of methyl propanoate, CH3CH2COOCH3, from methanol and propanoic acid.

A
  • CH3COOH + CH3CH2COOH - > CH3CH2COOCH3 + H2O
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4
Q

Name and outline a mechanism for the reaction between methanol and propanoyl chloride to form methyl propanoate.

A

Name of mechanism:

  • Nucleophilic addition-elimination

Mechanism:

  • ( CH3OH^- , with lone pair of electrons on the O, attacks the delta positive carbon attached to the O ( C = O ) )
  • ( Arrow is drawn from the lone pair on OH to the carbon )
  • ( Arrow is drawn from the double bond in C = O to the oxygen )
  • ( The oxygen now has a lone pair of electrons and a negative charge )
  • ( The double bond on the oxygen is reformed )
  • ( The Cl is broken off due to the reformation )
  • ( An arrow is drawn from the lone pair of electrons on the O to the bond between the C - O )
  • ( An arrow is drawn from the C - Cl bond to the Cl )
  • ( Due to the bonding of the CH3OH, the O gains a positive charge )
  • ( The H in the OH bond therefore breaks off as the electrons are attracted to the positive charge )
  • ( An arrow is drawn from the O - H bond to the O )
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5
Q

Propanoic anhydride can be used instead of propanoyl chloride in the preparation of methyl propanoate from methanol.
Draw the structure of propanoic anhydride.

A
  • CH3CH2COO
    CH3CH2COO
  • ( It’s a repeated molecule attached by the oxygen atom at the end of the molecule )
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6
Q

Give one advantage of the use of propanoyl chloride instead of propanoic acid in the laboratory preparation of methyl propanoate from methanol.

A
  • Faster
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7
Q

Give one advantage of the use of propanoic anhydride instead of propanoyl chloride in the industrial manufacture of methyl propanoate from methanol.

A
  • No corrosive HCl fumes formed
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8
Q

An ester contain a benzene ring.
The mass spectrum of this ester shows a molecular ion peak at M / Z = 136.
Deduce the molecular formula of this ester.

A
  • C6H6O2
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9
Q

Draw two possible structures for this ester.

C6H6O2

A
  • Benzene ring-COOCH3 ( On the right vertices )

- Benzene ring-OCOCH3 ( On the left vertices )

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10
Q

*Esters have many important commercial uses such as solvents and artificial flavourings in foods.
Esters can be prepared in several ways including the reactions of alcohols with carboxylic acids, acid anhydrides, acyl chlorides, and other esters.

Ethyl butanoate is used as a pineapple flavouring in sweets and cakes.
Write an equation for the preparation of ethyl butanoate from an acid and an alcohol.

Give a catalyst used for the reaction.

A
  • CH3CH2CH2COOH ( catalyst )
  • ( Butanoic acid )
  • CH3CH2OH - > CH3CH2CH2COOCH2CH3 + H2O
  • ( Ethanol - > Ethyl butanoate + water )
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11
Q

Butyl ethanoate is used as a solvent in the pharmaceutical industry.
Write an equation in preparation and ethanoic acid anhydride and an alcohol.

A
  • CH3CH2CH2CH2OH
  • ( Butanol )
  • ( CH3CO )2O - > CH3COOCH2CH2CH2CH3 + CH3COOH
  • ( Ethanoic anhydride - > Butyl ethanoate + ethanoic acid )
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12
Q

The ester shown below occurs in vegetable oils.
Write an equation to show the formation of biodiesel from this ester.

CH2OOCC17H31
                  |
   CHOOCC17H33
                  |
 CH2OOCC17H29
A
  • ( CH2OOCC17H31 CH2OH C17H31COOCH3 |
    |
    CHOOCC17H33 + 3CH3OH - > CHOH + C17H33COOCH3
    | |
    CH2OOCC17H29 ) CH2OH C17H29COOCH3
  • ( Look at your exam paper for a clearer answer )
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13
Q

The triester, T , shown below is found in Palm oil.
When T is heated with an excess of sodium hydroxide solution, the alcohol glycerol is formed together with a mixture of three other products as shown in the following equation.

CH2OOC( CH2 )14CH3
 |
CHOOC( CH2 )7CH = CH( CH2 )7CH3 + NaOH - >
 |
CH2OOC( CH2 )12CH3
          ( T )
                    CH3( CH2 )14COONa
CH2OH
 |                                    +
CHOH  +  CH3( CH2 )7CH = CH( CH2 )7COONa
 |                                    +
CH2OH
                    CH3( CH2 )12COONa

( Glycerol )

Give the IUPAC name for glycerol.

A
  • Propan-1, 2, 3-triol
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14
Q

Give a use for the mixture of sodium salts formed in this reaction.

( CH2OOC( CH2 )14CH3
 |
CHOOC( CH2 )7CH = CH( CH2 )7CH3 + NaOH - >
 |
CH2OOC( CH2 )12CH3
          ( T )
                    CH3( CH2 )14COONa
CH2OH
 |                                    +
CHOH  +  CH3( CH2 )7CH = CH( CH2 )7COONa
 |                                    +
CH2OH
                    CH3( CH2 )12COONa

( Glycerol ) )

A
  • Soap
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15
Q

When T is heated with an excess of methanol, glycerol is formed together with a mixture of methyl esters.
Give a use for this mixture of methyl esters.

( CH2OOC( CH2 )14CH3
 |
CHOOC( CH2 )7CH = CH( CH2 )7CH3 + NaOH - >
 |
CH2OOC( CH2 )12CH3
          ( T )
                    CH3( CH2 )14COONa
CH2OH
 |                                    +
CHOH  +  CH3( CH2 )7CH = CH( CH2 )7COONa
 |                                    +
CH2OH
                    CH3( CH2 )12COONa

( Glycerol ) )

A
  • Biodiesel
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16
Q

One of the other methyl esters in the mixture has the formula CH3( CH2 )12COOCH3.
Write an equation for the complete combustion of one molecule of this ester.

A
  • CH3( CH2 )12COOCH3 + 43 / 2O2 - > 15CO2 + 15H2O
17
Q

The three compound CH3CH2CH2CH2OH, ( CH3 )3COH and CH3 CH2CH2CHO can be distinguished by use of the following three reagents:

  1. Potassium dichromate( VI ) acidified with dilute sulphuric acid
  2. Tollens’ reagent
  3. Ethanoic acid, together with a small amount of concentrated sulfuric acid

Identify which of these three organic compounds would reduce acidified potassium dichromate( VI ).
Give the structures of the organic products formed.
Write equation for the reduction of dichromate( VI ) ions in acidic solution.

A
  • Potassium dichromate is reduced by CH3CH2CH2CH2OH
  • Oxidised to CH3CH2CH2CHO and CH3CH2CH2COOH
  • CH3CH2CH2CHO is oxidised to CH3CH2CH2COOH
  • Cr2O7^2+ + 14H^+ + 6e^- - > 2Cr^3+ + 7H2O
18
Q

Identify which one of these three compounds would reduce tollens’ reagent.
Give the structure of the organic product formed.
Write a half equation for the reduction of tollens’ reagent.

( The three compound CH3CH2CH2CH2OH, ( CH3 )3COH and CH3 CH2CH2CHO can be distinguished by use of the following three reagents:

  1. Potassium dichromate( VI ) acidified with dilute sulphuric acid
  2. Tollens’ reagent
  3. Ethanoic acid, together with a small amount of concentrated sulfuric acid )
A
  • Tollens’ reagent is reduced by CH3CH2CH2CHO
  • Oxidised to CH3CH2CH2COOH
  • [ Ag( NH3 )2 ]^+ + e^- - > Ag + 2NH3

Chemistry (13 decks)

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